Republished as still quite a big issue!
One of the main topics on the advice line recently has been the fitting of the bit. Often when I am speaking to a client, it sounds like they are in what should be the best design of bit for the horse and the level they are training at but somehow things just aren't going quite right. After all of the usual checks (dentist etc) have been ruled out, the next topic is does the bit actually fit? More often than not, it seems it doesn't.
If your horse is in a loose ring, say with a lozenge for example, and it is snatching and grabbing or leaning on one rein, it may just be worth checking that the bit is the right size and not too big. If too big, we often find that this can be quite uncomfortable for the horse, even if the bit is a very good design. If too big it could be sliding back and forth across the tongue and that is often the reason the horse tries to grab it and lean on it it; to keep it still and to stop the discomfort.
Too small a fit can lead to more obvious issues such as bruising and cuts to the inside of the cheek pouches, the lips and also externally at the lip curl. The horse can sometimes be accused of not wanting to take the rein forwards when the bit doesn't fit and once we understand why this is, at least it can be rectified with a good fitting bit and training can then be resumed.